The present invention relates to an optical disk replay device which replays information recorded upon an optical disk.
In an optical disk replay device, tracking servo for an optical pickup is performed according to a tracking error signal.
For example, when the objective lens shifts toward the inner side of a track upon the optical disk, then at this time, based upon a tracking error signal, the objective lens is shifted by the tracking servo towards the external side of the track. The tracking servo applies a tracking drive voltage to a tracking coil of a tracking actuator based upon the tracking error signal. By doing this, the objective lens is drive controlled so as to be kept in its normal position relative to the track. In other words, the tracking error balances is compensated so as to become zero.
As documents in which this type of technique is disclosed, Japanese Laid-Open Patent Publication 2003-123283 and Japanese Laid-Open Patent Publication 2005-310257 are cited.
However, when the objective lens shifts, the balance of the tracking error signal changes, since the positional relationship of the objective lens and the light receiving element deviates. With tracking servo control in which this balance change is ignored, there is the problem that drive control of the objective lens may not be performed adequately, and there is a possibility that tracking slippage may occur. In particular, since the balance characteristic during lens shifting is bad with a tracking error signal (PPTE) of the push-pull type, accordingly there has been the problem has arisen that this type of tracking slippage may occur frequently.
The present invention has been conceived in order to solve this type of problem, and takes as its objective to provide an optical disk replay device which is capable of enhancing the tracking accuracy for an optical pickup, by obtaining a relationship between a tracking error signal and a tracking drive signal.